Encrypt Password

Public Shared Function Encriptar(ByVal cleanString As String) As String
Dim clearBytes As [Byte]()
clearBytes = New UnicodeEncoding().GetBytes(cleanString)
Dim hashedBytes As [Byte]() = CType(CryptoConfig.CreateFromName("MD5"),
HashAlgorithm).ComputeHash(clearBytes)
Dim hashedText As String = BitConverter.ToString(hashedBytes)
Return hashedText
End Function

this function encrypt user password, I need to un-encrypt that password